固体酸磷酸硼酸性调控及催化环氧树脂成炭机理研究

In the cases of polymer flame retardance by catalyzing char-formation in the condensed phase, the rate of crosslinking and charring, as well as quantity and thermo-oxidation resistance of the obtained char residue depend on the chemical reactions and physical actions during thermal degradation process, and these parameters determine the flame retardant efficiency. The composition, structure and acidity of the char-forming flame retardants are the key factors influencing the chemical reactions and physical actions of catalyzing charring during polymer thermal degradation. In our previous study, it has been realized that by regulating the composition, structure and acidity of boron phosphate, epoxy/boron phosphate hybrids performed differently in flammability, suggested by remarkably different intumescent charring behaviors. During combustion, boron phosphate acted as a catalyst to promote the formation of graphitic and ceramic-like char. Based on these results, it's proposed here to further carry on the following study: synthesize boron phosphates with regulated acidities by using different molar ratios of B/P and various calcination temperatures , discuss the effect of regulations on the acidity and distribution of Br?nsted acid and Lewis acid of the resultant boron phosphate; investigate the effect of acidity, acid sites distribution and loading of boron phosphate on thermal degradation, combustion and intumescent charring behavior of epoxy/boron phosphate hybrids, in order to explore the relationship of acidity and acid sites distribution of boron phosphate between its catalytic performance on crosslinking, graphic and ceramic-like charring reaction; demonstrate the flame retardant mechanism of boron phosphate by hydroxyl groups elimination, water release, aromatic and olefin moieties crosslinking and catalyzing carbonization of mode compounds. This research may not only be crucial to understand the fundamentals of polymer flame retardancy by catalyzing carbonization, but also contribute to stimulate studies on synergistic non-halogen condensed-phase flame retardancy and the design and application of char-forming flame retardants. Keywords: Boron phosphate; Acidity; Catalyzing carbonization; Flame retardancy; Composites

阻燃聚合物燃烧过程的成炭速度、成炭量及炭层的耐热氧化程度，受制于热降解过程的化学与物理作用，并强烈影响着阻燃效率。催化成炭阻燃剂的组成、结构、酸度及其分布是影响聚合物热降解成炭化学反应及物理作用的关键。我们前期研究表明，调控磷酸硼的酸度及分布，阻燃环氧树脂复合材料的燃烧性能差异明显，出现了显著不同的膨胀成炭现象，且形成了类石墨及类陶瓷炭层。因此，本项目拟采用磷酸硼作为催化成炭阻燃剂，利用改变B/P摩尔比及煅烧温度，调控B酸和L酸的酸性位数量及比例，制备酸性不同的磷酸硼；探讨磷酸硼的酸度及其分布对环氧树脂复合材料燃烧、热降解及膨胀成炭行为的影响规律，建立磷酸硼酸性与环氧树脂热降解反应及成炭反应的关系；采用模型化合物对本项目假设的磷酸硼催化EP热降解过程中羟基脱除及释水、芳香及烯烃产物交联、膨胀成炭的阻燃机理进行验证。该研究对催化成炭阻燃聚合物机理研究及催化成炭阻燃剂的设计均具有重要意义。

阻燃聚合物材料是产业和社会发展的火安全保障，以低烟无毒环境友好为特征的凝聚相阻燃技术是材料科学研究的前沿热点。阻燃聚合物燃烧过程中的成炭速度、成炭量及炭层结构，受制于热降解过程的化学与物理作用，并强烈影响着凝聚相的阻燃效率。催化成炭阻燃剂的组成、结构、酸度及其分布是影响聚合物热降解成炭化学反应及物理作用的关键。.本项目开展了五方面的研究：固体酸纳米磷酸硼（BP）的制备及酸性表征；环氧树脂复合材料（EP/BP）固化行为及力学性能研究；BP酸性及其分布对成炭速度、成炭量及炭层组成结构的影响；BP酸性及其分布对热降解气相及凝聚相产物组成结构的影响；催化成炭热降解反应的验证及拓展应用研究。得到了如下重要结果和关键数据：.实现了BP的酸性调控。通过改变硼/磷摩尔比（B/P=1.25、1和0.8）及产物煅烧温度制备了表面B酸和L酸比例（B/L）不同的BP：BP1.25（1.27）＞BP1（0.40）＞BP0.8（0.35）。BP表面酸性及B/L随B/P值的减小及煅烧温度的升高而降低。.BP对EP复合材料固化行为及力学性能研究表明，BP具有显著催化固化过程链增长反应的作用。MCNTs与BP复合可以改善材料的力学性能。BP酸性与复合材料燃烧性能及成炭参数联系的研究表明，BP的酸性位点越多，B酸或L酸越多，氧指数越高：BP1.25（29.4%）＞BP0.8（28.7%）＞BP1（28.3%）；热释放及烟释放越低；成炭速度越快、成炭量及石墨化程度越高。EP/BP1.25的成炭速度是EP的2.3倍，700℃的残炭量较计算值高80%。.热降解气相及凝聚相产物研究表明，BP表面酸性更强，B酸位点居多时，以脱H2O反应为主；L酸位点居多时，以脱氢反应为主。由此，建立了催化成炭机理模型，并通过模型化合物给予了验证。拓展研究结果指出，BP具有催化聚氨酯泡沫热解产物交联成炭作用，具有催化碳纤维前驱体聚丙烯腈/木质素类石墨结构转变作用。.本研究的科学意义在于，可以通过调控磷酸硼表面酸性及其分布实现对环氧树脂复合材料热降解产物的催化成炭速度、成炭量及阻燃性能的控制；为催化成炭阻燃剂的设计及提高材料的阻燃性能提供了理论依据。